Authorities say that the 33-year-old began fighting with Jose Paul Vasquez Flores, 36, and that Flores stabbed him. Another stabbing took place a week earlier on a different Metro train.

A 33-year-old man was in critical but stable condition Saturday after being stabbed during what began as a fistfight on the Metro Gold Line as it traveled through Pasadena, authorities said.

The violence Friday evening came on the heels of a fatal stabbing the week before on a Metro Red Line train. That stabbing also followed a fight and was the first slaying on the subway since it began operations in 1993.

The latest attack took place aboard a northbound Gold Line train about 6:30 p.m. Friday. Authorities said that the victim, whose name was not released, began fighting with Jose Paul Vasquez Flores, 36, and that Flores stabbed him.

About 100 passengers were aboard the train at the time, Metro spokeswoman Helen Ortiz-Gilstrap said. When the train reached the Memorial Park station, it was met by Pasadena police, firefighters and deputies from the Los Angeles County Sheriff's Department, which is responsible for security on the trains.

All passengers were evacuated except for witnesses, who were interviewed by authorities.

The victim was taken to a nearby hospital, where he underwent surgery.

Flores was treated for injuries and arrested on suspicion of assault with a deadly weapon. His bail was set at $1 million, the department said. A bloody knife was recovered from his pants pocket, authorities said.

The station closed for the rest of the evening, although one track was opened about 10:15 p.m. so trains could pass through, Ortiz-Gilstrap said.

Last week sheriff's deputies arrested Gene Sim, 33, in connection with the killing of Jesse Garay, 59, of North Hollywood on the Red Line on Aug. 19. Authorities described Sim as a transient.

Witnesses, including a Los Angeles Times staff writer, said a confrontation broke out on the crowded subway car when Garay began swinging a chain at Sim, who then pulled out a knife.

Sim asked fellow passengers to back up his claim of self-defense, then fled the Red Line train after it came to a stop at the Hollywood/Vine station, according to Todd Martens, the Times staff writer who witnessed the attack.

The Sheriff's Department has beefed up patrols on the Red and Gold lines, Metro officials said.

Anyone with information about the stabbing on the Gold Line is asked to call sheriff's Metro Transit Services detectives at (323) 563-5000.